HEMPSTEAD, Texas -- Twenty percent of Hempstead's police officers were suspended after felony indictments were issued against them, KPRC Local 2 exclusively reported Monday.

The Hempstead Police Department only has 13 officers.

KPRC Local 2 broke the story in 2004 when members of the Cypress Creek EMS Tactical Medics Unit were accused of setting off SWAT team grenades just for fun.

The first flash-bang grenade blew up under a police car at a Hempstead truck stop, sending police running out with guns.

"That would have been very scary," truck stop manager Mohammad Khan said. "Thank God there was no customer at that time."

Hempstead's police chief promised he would investigate, but then the same reserve officer was accused of setting another grenade off at a back-yard party.

One party guest lost a foot.

Two full-time officers and five reserve officers have been charged with felony evidence tampering, accused of trying to cover it up.

"Physical evidence at the scene, as alleged in the indictment, is the removal of physical evidence and cleaning up of a potential crime scene," Montgomery County Fire Marshal Jimmy Williams said.

The fire marshal said 91 of the SWAT team grenades were confiscated from the Cy-Creek firehouse where most of the men were on a team of tactical medics.

Brad England, the head of Cy-Creek EMS, is among those charged.

The fire marshal said all of the confiscated grenades were unregistered or they were registered as far away as Connecticut, with police departments that never heard of the accused men.

"They had no knowledge," Williams said. "They never had possession of those and had no knowledge of why they'd be registered to them."

Gene Williams, the tactical medic accused of setting off both grenades, was charged with felony assault and evidence tampering.

Williams turned himself in on Monday.

Reserve officers Wren Nealy, Leeland Miller and Nick Robbins turned themselves in Tuesday. They have all posted bond.

England, along with full-time officers David Schmidt and Jason Martinez, have warrants out for their arrest.

Gene Williams was fired from the Hempstead police force, but he remained on duty at Cy-Creek EMS after the first grenade prank.

Hempstead's police chief said it could be a while for these cases to wrap through the court system. He is checking with city leaders to determine how he should deal with so many suspended officers.